This project is aimed toward the development of a theory of hydrogen bonding, to be established by analyzing the results of ab initio self-consistent field molecular orbital calculations on various series of hydrogen-bonded dimers, and on some larger hydrogen-bonded polymers. Some specific goals of this work are: 1) to determine the equilibrium structures and energies of various series of hydrogen-bonded dimers, and to characterize the chemical moieties which act either as proton donors or proton acceptors in these series; 2) to identify, and evaluate the relative importance of, primary and secondary factors in determining equilibrium dimer structures and hydrogen bond energies, and to examine substituent effects on the hydrogen bond; 3) to compute and analyze various properties of equilibrium dimers, making correlations with experimental data where possible, and noting the implications for hydrogen bonding in important biological systems; 4) to examine inter- and intramolecular proton transfer in hydrogen-bonded systems; 5) to further investigate pi hydrogen bonding; 6) to examine nonadditivity effects in hydrogen-bonded trimers; and 7) to further test and refine the General Hybridization Model for the hydrogen bond, and to work toward the formulation of new models for analyzing hydrogen bonding in complex biological systems.